Gas Chromatography (GC) – Basics

Gas Chromatography (GC) is a core analytical technique used in refineries, petrochemical plants, gas processing units, and power plants. This learning path explains GC fundamentals in the same sequence technicians encounter them in the field.

GC Working Principle – Basic Flow

A GC analyzer separates gas components inside a column based on their physical and chemical properties. Each component reaches the detector at a different time, forming a chromatogram.

Sample Gas Injection Valve Column Detector

GC Learning Path

Beginner

GC Sampling System

Probes, filters, regulators, conditioning — the source of most GC problems.

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Beginner

6-Port Sampling Valve

LOAD vs INJECT positions and internal valve logic.

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Intermediate

Timing vs Chromatogram

How valve timing directly affects peaks and retention time.

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Intermediate

GC Backflush Operation

Removing heavy components to protect the column and reduce cycle time.

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Advanced

Heart-Cut (Dual Column)

Selectively transferring target components for better separation.

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Advanced

Full GC Cycle

End-to-end analyzer sequence from purge to ready state.

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All Levels

GC Failure Modes

Symptom → root cause → corrective action mapping.

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Technician Rule

If a GC analyzer misbehaves, always start upstream: sampling → pressure → valves → timing. Electronics and columns are rarely the first failure point.